U.S. patent application number 13/951371 was filed with the patent office on 2013-11-21 for mobile station, base station, transmitting method and receiving method.
This patent application is currently assigned to PANASONIC CORPORATION. The applicant listed for this patent is PANASONIC CORPORATION. Invention is credited to Sadaki FUTAGI, Ayako HORIUCHI, Daichi IMAMURA, Yoshihiko OGAWA.
Application Number | 20130308583 13/951371 |
Document ID | / |
Family ID | 38609363 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130308583 |
Kind Code |
A1 |
OGAWA; Yoshihiko ; et
al. |
November 21, 2013 |
MOBILE STATION, BASE STATION, TRANSMITTING METHOD AND RECEIVING
METHOD
Abstract
A radio communication base station device can efficiently obtain
a multiuser diversity gain from frequency scheduling while reducing
the amount of a reference signal occupying an uplink. In the
device, a grouping section divides a plurality of RBs (Resource
Blocks) into a plurality of RB groups. An RB group control unit
performs a control to change the correspondence relationship
between the RBs and the RB groups with time. When the grouping
section divides the RBs into the RB groups, the RB control unit
performs a control to change a combination of the RBs included in
each of the RB groups with time. A scheduling section performs a
scheduling of allocating each of a plurality of mobile stations to
each of the RBs in each of the RB groups according to the reception
quality of the reference signal.
Inventors: |
OGAWA; Yoshihiko; (Kanagawa,
JP) ; IMAMURA; Daichi; (Kanagawa, JP) ;
HORIUCHI; Ayako; (Kanagawa, JP) ; FUTAGI; Sadaki;
(Ishikawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PANASONIC CORPORATION |
Osaka |
|
JP |
|
|
Assignee: |
PANASONIC CORPORATION
Osaka
JP
|
Family ID: |
38609363 |
Appl. No.: |
13/951371 |
Filed: |
July 25, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12295260 |
Sep 29, 2008 |
|
|
|
PCT/JP2007/056950 |
Mar 29, 2007 |
|
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13951371 |
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04L 5/006 20130101;
H04W 88/085 20130101; H04L 5/023 20130101; H04L 5/0037 20130101;
H04W 72/1289 20130101; H04L 5/0085 20130101; H04L 5/0007
20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/12 20060101
H04W072/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2006 |
JP |
2006-099914 |
Claims
1. A mobile station device comprising: a receiving section
configured to receive first information related to one of groups,
into which a plurality of resource blocks are grouped, and to
receive second information indicating a resource block, which is
included in said one of the groups and which is assigned to the
mobile station device; and a transmitting section configured to
transmit data on the resource block assigned to the mobile station
device based on the first information and the second
information.
2. The mobile station device according to claim 1, wherein said
transmitting section is further configured to transmit a reference
signal on resource blocks included in said one of the groups based
on the first information.
3. The mobile station device according to claim 1, wherein resource
blocks grouped into each of the groups are changed over time.
4. The mobile station device according to claim 1, wherein a
resource block included in said one of the groups are not changed
over time.
5. The mobile station device according to claim 1, wherein resource
blocks grouped into each of the groups are changed over time, while
a resource block included in said one of the groups are not changed
over time.
6. A base station device comprising: a transmitting section
configured to transmit first information related to one of groups,
into which a plurality of resource blocks are grouped, and to
transmit second information indicating a resource block, which is
included in said one of the groups and which is assigned to a
mobile station; and a receiving section configured to receive data,
which is transmitted from the mobile station on the resource block
assigned to the mobile station based on the first information and
the second information.
7. The base station device according to claim 5, wherein said
receiving section is further configured to receive a reference
signal, which is transmitted from the mobile station on resource
blocks included in said one of the groups based on the first
information.
8. The base station device according to claim 5, wherein resource
blocks grouped into each of the groups are changed over time.
9. The base station device according to claim 5, wherein a resource
block included in said one of the groups are not changed over
time.
10. The base station device according to claim 5, wherein resource
blocks grouped into each of the groups are changed over time, while
a resource block included in said one of the groups are not changed
over time.
11. A transmitting method comprising: receiving, at a mobile
station, first information related to one of groups, into which a
plurality of resource blocks are grouped; receiving,at the mobile
station, second information indicating a resource block, which is
included in said one of the groups and which is assigned to the
mobile station, the first information and the second information
being transmitted from a base station to the mobile station; and
transmitting, from the mobile station to the base station, data on
the resource block assigned to the mobile station based on the
first information and the second information.
12. A receiving method comprising: transmitting, from a base
station to a mobile station, first information related to one of
groups, into which a plurality of resource blocks are grouped;
transmitting, from the base station to the mobile station, second
information indicating a resource block, which is included in said
one of the groups and which is assigned to the mobile station; and
receiving, at the base station, data, which is transmitted from the
mobile station on the resource block assigned to the mobile station
based on the first information and the second information.
13. An integrated circuit for controlling a process comprising:
receiving, at a mobile station, first information related to one of
groups, into which a plurality of resource blocks are grouped;
receiving, at the mobile station, second information indicating a
resource block, which is included in said one of the groups and
which is assigned to the mobile station, the first information and
the second information being transmitted from a base station to the
mobile station; and transmitting, from the mobile station to the
base station, data on the resource block assigned to the mobile
station based on the first information and the second
information.
14. An integrated circuit for controlling a process comprising:
transmitting, from a base station to a mobile station, first
information related to one of groups, into which a plurality of
resource blocks are grouped; transmitting, from the base station to
the mobile station, second information indicating a resource block,
which is included in said one of the groups and which is assigned
to the mobile station; and receiving, at the base station, data,
which is transmitted from the mobile station on the resource block
assigned to the mobile station based on the first information and
the second information.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation application of application Ser. No.
12/295,260 filed Sep. 29, 2008, which is a 371 application of
PCT/JP2007/056950 filed Mar. 29, 2007, which is based on Japanese
Application No. 2006-099914 filed Mar. 31, 2006, the entire
contents of each of which are incorporated by reference herein.
TECHNICAL FIELD
[0002] The present invention relates to a radio communication
mobile station apparatus (hereinafter simply "mobile station") that
transmits a reference signal and a radio communication base station
apparatus (hereinafter simply "base station") that carries out
scheduling based on the received quality of the reference
signal.
BACKGROUND ART
[0003] A multicarrier transmission system where communication is
carried out using a plurality of frequency carriers, frequency
scheduling is performed taking into account the frequency
selectivity of multipath fading channels to improve throughput.
[0004] For efficient uplink frequency scheduling, abase station
needs to learn the received qualities of all resource blocks
(hereinafter simply "RB's") in all mobile stations and so all
mobile stations need to transmit reference signals using all RB's.
A reference signal refers to a known signal set in advance between
the base station and the mobile stations or a signal according to
this known signal. Further, a reference signal is also referred to
as a "pilot signal."
[0005] FIG. 1 shows a conventional scheduling method. The base
station measures the received quality of each RB using the
reference signals transmitted from mobile stations A and B and
assigns RB's for data transmission to mobile stations A and B based
on the received qualities (see, for example, Non-Patent Document
1).
[0006] Non-Patent Document 1: "Investigations on Packet Scheduling
Exploiting Frequency Selectivity in Uplink Radio Access," Yoshiaki
Ofuji, AkihitoMorimoto, Kenichi Higuchi, Mamoru Sawahashi, the
Institute of Electronics, Information and Communication Engineers
Society Conference, B-5-51, pp 451, March 2005.
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0007] However, according to the conventional scheduling method,
all mobile stations need to transmit reference signals per subframe
using all RB's, and so the amount of reference signals occupying
the uplink increases following the increase in the number of mobile
stations. As a result, the region for data transmission becomes
smaller and throughput decreases (see FIG. 2).
[0008] It is therefore an object of the present invention to
provide a base station and mobile station that are able to reduce
the amount of reference signals occupying the uplink and
efficiently achieve multiuser diversity gain by frequency
scheduling.
Means for Solving the Problem
[0009] The base station according to the present invention employs
a configuration including: a grouping section that divides a
plurality of RB's into a plurality of groups; a scheduling section
that, in the plurality of groups, carries out scheduling to assign
a plurality of mobile stations to the plurality of RB's based on
received qualities of reference signals transmitted from the
plurality of mobile stations; a controlling section that changes
correspondences between the plurality of RB's and the plurality of
groups over time; and a transmitting section that transmits a
report of a scheduling result to the plurality of mobile
stations.
[0010] The mobile station according to the present invention
employs a configuration including: a receiving section that
receives a report of a scheduling result from the base station; and
a transmitting section that transmits a reference signal using a RB
in a group to which the mobile station belongs out of a plurality
of groups, to the base station and transmits data using a RB
matching the scheduling result, to the base station.
Advantageous Effect of the Invention
[0011] According to the present invention, abase station groups a
plurality of RB's and carries out scheduling on a per RB group
basis to assign RB's to the mobile stations, so that it is possible
to reduce the amount of reference signals compared to a case where
grouping is not carried out. Further, given that each group employs
a unique assignment of RB's, the scheduling result of a given group
does not influence the scheduling results of other groups, so that
each mobile station can be assigned in a reliable manner to one of
RB's where reference signals have been transmitted. Further, by
changing the correspondences between a plurality of RB's and a
plurality of groups over time, the RB that each mobile station can
refer to changes, so that it is possible to efficiently achieve
multiuser diversity gain. Furthermore, each mobile station
transmits the reference signal by limiting RB's to the RB's
included in a group to which the mobile station belongs, thereby
reducing the amount of reference signals transmitted in each
subframe.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 shows a conventional scheduling method;
[0013] FIG. 2 shows the relationship between the number of mobile
stations and the amount of reference signals in the conventional
scheduling method;
[0014] FIG. 3 is a block diagram showing a configuration of a base
station according to Embodiment 1;
[0015] FIG. 4 is a specific example of RB group information
according to Embodiment 1;
[0016] FIG. 5 is a block diagram showing a configuration of a
mobile station according to Embodiment 1;
[0017] FIG. 6 is an operation sequence according to Embodiment
1;
[0018] FIG. 7 is an operation diagram of a communication system
according to Embodiment 1;
[0019] FIG. 8 is an illustrative diagram of RB assignment
information according to Embodiment 1;
[0020] FIG. 9 is a block diagram showing a configuration of the
base station according to Embodiment 2;
[0021] FIG. 10 is an operation diagram of the communication system
according to Embodiment 2;
[0022] FIG. 11 is a block diagram showing a configuration of the
base station according to Embodiment 3;
[0023] FIG. 12 is an example of a table according to Embodiment
3;
[0024] FIG. 13 is another example of a table according to
Embodiment 3;
[0025] FIG. 14 is a block diagram showing a configuration of the
base station according to Embodiment 4;
[0026] FIG. 15 is a block diagram showing a configuration of the
mobile station according to Embodiment 5;
[0027] FIG. 16 is an operation diagram of the communication system
according to Embodiment 5; and
[0028] FIG. 17 is an operation diagram of the communication system
according to Embodiment 6.
BEST MODE FOR CARRYING OUT THE INVENTION
[0029] Embodiments of the present invention will be described in
detail below with reference to the accompanying drawings. With the
following embodiments, the band used for the uplink is divided into
a plurality of RB's, and a mobile station communicates with a base
station using one or a plurality of RB's.
Embodiment 1
[0030] FIG. 3 is a block diagram showing a configuration of base
station 100 according to the present embodiment.
[0031] RF receiving section 101 carries out predetermined radio
reception processing such as down-conversion and A/D conversion on
a signal received through antenna 115 and outputs the signal to CP
removing section 102.
[0032] CP removing section 102 removes the CP (Cyclic Prefix)
portion from the signal outputted from RF receiving section 101
based on the synchronization timing and outputs the signal to
separating section 103.
[0033] Separating section 103 separates the signal outputted from
CP removing section 102 to the reference signal and a data/control
signal, and outputs the reference signal to received quality
measuring section 107 and the data/control signal to frequency
domain equalizing section 104.
[0034] Frequency domain equalizing section 104 compensates the
distortion of the signal outputted from separating section 103 per
one block length by equalizing the distortion in the frequency
domain and outputs the compensated signal to demodulating section
105.
[0035] Demodulating section 105 carries out a constellation point
decision on the data/control signal and outputs the signal after
the decision to decoding section 106.
[0036] Decoding section 106 obtains received data by performing
error correcting processing.
[0037] Received quality measuring section 107 measures the received
quality of each RB per mobile station using the reference signal
outputted from separating section 103 and reports the measurement
result to scheduling section 110.
[0038] Grouping section 109 groups a plurality of RB's into a
plurality of RB groups. By this grouping processing, a plurality of
RB groups and the RB's included in these RB groups are determined.
Hereinafter, information showing the correspondences between RB's
and RB groups will be referred to as "RB group information." RB
group information is outputted to scheduling section 110 and
encoding section 111.
[0039] FIG. 4 shows a specific example of RB group information. In
this example, nine RB's (RB1 to RB9) are divided into three RB
groups of group .alpha., group .beta. and group .gamma., and RB1 to
RB3 are grouped into group .alpha., RB4 to RB6 are grouped into
group .beta. and RB7 to RB9 are grouped into group .gamma..
[0040] RB group controlling section 108 carries out a control for
changing the correspondences between a plurality of RB's and a
plurality of RB groups over time. To be more specific, when
grouping section 109 groups a plurality of RB's into a plurality of
RB groups, RB group controlling section 108 carries out a control
for changing the combinations of RB's included in a plurality of RB
groups overtime. By this control, the RB's included in each RB
group are not fixed and rearranged over time.
[0041] Scheduling section 110 carries out scheduling for assigning
a plurality of mobile stations to a plurality of RB's in RB groups
based on the received qualities reported from received quality
measuring section 107. The reference signal from each mobile
station inputted to received quality measuring section 107 is
transmitted by limiting RB's based on the reported RB group
information, and so scheduling section 110 specifies the RB's
included in each RB group according to this RB group information,
carries out scheduling individually for each RB group and assigns
the RB for data transmission to each mobile station. Hereinafter,
information showing the correspondences between a plurality of
mobile stations and the RB's assigned to these mobile stations will
be referred to as "RB assignment information." RB assignment
information is outputted to encoding section 111.
[0042] Encoding section 111 performs error correcting encoding
processing on the transmission data, control signal, RB group
information and RB assignment information that are inputted.
[0043] Modulating section 112 modulates data sequences to be
inputted by modulation schemes such as PSK modulation and QAM
modulation.
[0044] CP adding section 113 generates the CP by copying a
predetermined portion from the rear end of the data sequence
outputted from modulating section 112 and adds the generated CP to
the head of the block.
[0045] RF transmitting section 114 carries out predetermined radio
transmission processing such as D/A conversion and up-conversion on
the signal outputted from CP adding section 113 and transmits the
signal through antenna 115.
[0046] In this way, base station 100 divides a plurality of RB's
into a plurality of RB groups, carries out scheduling for assigning
a plurality of mobile stations to a plurality of RB's based on the
received qualities of reference signals transmitted from a
plurality of mobile stations and reports the scheduling result to a
plurality of mobile stations. Then, base station 100 changes the
correspondences between a plurality of RB's and a plurality of RB
groups over time.
[0047] By this means, scheduling is performed by limiting each RB
group and each mobile station group has only to transmit reference
signals using RB's included in the RB group to which each mobile
station belongs, so that it is possible to decrease the number of
reference signals occupying the uplink. Further, given that
scheduling is carried out individually per RB group, the scheduling
result of a given RB group does not influence the scheduling
results of other RB groups, and each mobile station can be assigned
in a reliable manner to one of RB's where the reference signals
have been transmitted, so that all mobile stations are able to
build stable communication. Further, by changing the
correspondences between a plurality of RB's and a plurality of RB
groups over time, the RB's included in each RB group change, so
that the RB to which each mobile station can be assigned changes
over time. Consequently, it is possible to efficiently achieve
multiuser diversity gain.
[0048] FIG. 5 is a block diagram showing a configuration of mobile
station 200 according to the present embodiment.
[0049] RF receiving section 201 carries out predetermined reception
processing such as down-conversion and A/D conversion on the signal
received through antenna 214 and outputs the signal to CP removing
section 202.
[0050] CP removing section 202 removes the CP portion from the
signal outputted from RF receiving section 201 based on the
synchronization timing and outputs the signal to frequency domain
equalizing section 203.
[0051] Frequency domain equalizing section 203 compensates the
distortion of the signal outputted from CP removing section 202 by
equalizing the distortion per one block length in the frequency
domain and outputs the compensated signal to demodulating section
204.
[0052] Demodulating section 204 carries out a constellation point
decision on the data/the control signal and outputs the signal
after the decision to decoding section 205.
[0053] Decoding section 205 performs error correcting processing to
obtain received data, the control signal, RB group information and
RB assignment information.
[0054] Based on the reported RB group information, reference signal
arranging section 206 arranges a reference signal in the RB in the
RB group to which the mobile station belongs.
[0055] Further, when deciding to which RB group the mobile station
belongs, reference signal arranging section 206 may use, for
example, the RB group including the RB in which data is currently
transmitted as the RB group to which the mobile station belongs. By
specifying the RB group to which the mobile station belongs in this
way, the reference signal is transmitted using a plurality of RB's
including the RB in which the data is currently transmitted.
Consequently, the base station refers to the received quality of
the current RB and the received qualities of other RB's and then
carries out scheduling per RB group, so that it is possible to
achieve greater throughput than the current throughput in all RB
groups. Further, in what order each mobile station arranges the
reference signal in the RB included in the RB group is set in
advance.
[0056] CP adding section 207 generates the CP by copying a
predetermined portion from the rear end of the reference signal
outputted from reference signal arranging section 206 and adds the
generated CP to the head of the block. RB specifying section 208
specifies the RB's for data transmission. To be more specific, RB
specifying section 208 specifies RB's in which transmission data
and control signals are arranged, based on the combination of RB
group information and RB assignment information. Further, the RB
group information used then is the RB group information used when
scheduling is carried out to generate RB assignment
information.
[0057] Encoding section 209 arranges the transmission data and
control signals that are inputted, in the RB's specified in RB
specifying section 208 and performs error correcting encoding
processing.
[0058] Modulating section 210 modulates transmission data sequences
outputted from encoding section 209 by modulation schemes such as
PSK modulation and QAM modulation.
[0059] CP adding section 211 generates the CP by copying a
predetermined portion from the rear end of the signal outputted
from modulating section 210 and adds the generated CP to the head
of the block.
[0060] Multiplexing section 212 time-multiplexes the reference
signal outputted from CP adding section 207 and the data signal
outputted from CP adding section 211, and then outputs the result
to RF transmitting section 213.
[0061] RF transmitting section 213 carries out predetermined radio
transmission processing such as D/A conversion and up-conversion on
the signal outputted from multiplexing section 212 and transmits
the signal through antenna 214.
[0062] In this way, mobile station 200 receives a report of the
scheduling result and a report of the correspondences between a
plurality of RB's and a plurality of RB groups from the base
station, transmits the reference signal using RB's in the RB group
in a plurality of RB groups to which mobile station 200 belongs and
transmits data using RB's according to the scheduling result, to
base station 100.
[0063] By limiting RB's for transmitting reference signals as
described above, it is possible to reduce the amount of reference
signals. Further, by changing RB group information periodically
(for example, per subframe or over a plurality of subframes), it is
possible to transmit reference signals periodically from mobile
stations using different RB's and efficiently achieve multiuser
diversity gain.
[0064] Next, FIG. 6 shows the operation sequence according to the
present embodiment.
[0065] Base station 100 sets the first RB group in ST11 and reports
this RB group information to mobile station 200.
[0066] In ST12, mobile station 200 transmits a reference signal
using RB's in the RB group to which mobile station 200 belongs and
which is indicated by the RB group information.
[0067] Base station 100 measures the received quality of the
reference signal transmitted from each mobile station and assigns
the RB for transmitting uplink data in ST13, and reports this RB
assignment information to mobile station 200. Further, base station
100 rearranges and resets the RB groups in ST14, and reports new RB
group information to mobile station 200.
[0068] Mobile station 200 transmits data based on RB assignment
information in ST15. Further, mobile station 200 transmits the
reference signal based on RB group information in ST16.
[0069] The processing in ST17 is the same as the processing in
ST13, and the processing in ST18 is the same as the processing in
ST14.
[0070] In this way, with the present embodiment, the
correspondences between RB's and RB groups are changed
periodically.
[0071] Next, the operation of the communication system according to
the present embodiment will be described using FIG. 7.
[0072] As described above, the present embodiment limits RB's for
transmitting reference signals to the RB's in an RB group reported
from the base station, the combination of RB's forming this RB
group is changed periodically. The following description assumes
that the number of RB's is four, the number of mobile stations is
four and the number of RB groups is two, and each mobile station
transmits the reference signal using two of four RB's. In FIG. 7,
in subframe 1, RB1 and RB2 form the first RB group and RB3 and RB4
form the second RB group. At times Tn and Tn+1, each mobile station
transmits the reference signal by limiting RB's to the RB included
in the RB group. That is, mobile station A and mobile station B
transmit reference signals by limiting RB's to RB1 and RB2, and
mobile station C and mobile station D transmit reference signals by
limiting RB's to RB3 and RB4.
[0073] Further, in FIG. 7, the number of RB's in the RB group is
two, and so reference signals are transmitted twice at times Tn and
Tn+1 in one subframe. However, the time for transmitting reference
signals is not limited to these two times.
[0074] Next, the base station compares the received quality of each
RB group measured using the reference signal transmitted from each
mobile station and determines the RB for data transmission to be
assigned to each mobile station. The RB for data transmission is
determined from one of the RB's in the RB group to which each
mobile station belongs. For example, in FIG. 7, RB1 and RB2 form
one RB group in subframe 1, and so RB's for data transmission are
assigned to RB1 and RB2 for mobile station A and mobile station
B.
[0075] In this case, to compare the received qualities, a method of
comparing the total SINR of each RB group and selecting an RB
arrangement of a high total SINR and other method may be used. In
subframe 1 in FIG. 7, by comparing received quality 1 at time Tn
(i.e. the total SINR value obtained by adding the SINR of RB1 in
mobile station A and the SINR of RB2 in mobile station 2) and
received quality 2 at time Tn+1 (i.e. the total SINR value obtained
by adding the SINR of RB1 in mobile station B and the SINR of RB2
in mobile station A), arrangement of mobile stations of the greater
total SINR value is used for an arrangement of the RB for data
transmission in subframe 2. If received quality 2 is greater than
received quality 1, the RB's for data transmission in subframe 2
are arranged as in the arrangement for received quality 2, that is,
mobile station B is assigned to RB1 and mobile station A is
assigned to RB2. The same comparison is drawn in the RB group of
RB3 and RB4, and arrangement of the RB's for data transmission is
determined for mobile stations. In this way, with the present
embodiment, in each of a plurality of RB groups, scheduling is
carried out so as to maximize the addition result of the SINR's of
the reference signals of a plurality of mobile stations.
[0076] Further, the priority may be set to each mobile station and
the SINR may be weighted according to the priority. Further, RB's
may be assigned to mobile stations per RB group in order from a
higher priority. Further, the priority of each mobile station may
be set according to the QoS (Quality of Service) of transmission
data of each mobile station, the moving speed of each mobile
station, the distance between the base station and each mobile
station, the number of mobile stations in the communication system,
the CQI (Channel Quality Indicator) of each mobile station and the
average CQI. By carrying out scheduling taking into account
priorities in this way, more flexible and adequate RB assignment is
possible.
[0077] Next, the base station reports RB assignment information
showing an RB for data transmission as the scheduling result, to
each mobile station. Each mobile station specifies the RB for data
transmission based on RB assignment information. Then, each mobile
station assigns data to this RB for data transmission and transmits
this data. Further, RB assignment information is generated for each
RB group where the reference signal has been transmitted in an
earlier subframe, and so a mobile station is able to learn the RB
for data transmission by utilizing the RB group information of the
earlier subframe.
[0078] The sequence of these operations is repeated periodically
(for example, per subframe or over a plurality of subframes)
changing the combination of RB's forming an RB group. That is, in
FIG. 7,while, in subframe 1, RB1 and RB2 form the first RB group
and RB3 and RB4 form the second group, in subframe 2, RB1 and RB3
form the first RB group and RB2 and RB4 form the second RB group.
In this way, with the present embodiment, the above operation is
repeated by rearranging the combination of RB's forming each RB
group.
[0079] As described above, it is possible to reduce the amount of
reference signals in each subframe by limiting transmission of
reference signals to RB groups, and is possible to effectively
achieve multiuser diversity gain by rearranging the combination of
RB's forming each RB group periodically. Further, by resetting RB
group information periodically and repeating the above processing,
an arrangement of the RB for transmission data is updated over
time, so that it is possible to track the RB for data transmission
supporting the fluctuation over time.
[0080] FIG. 8 is an illustrative diagram of RB assignment
information. RB assignment information is generated per RB group in
the base station using RB group information.
[0081] The base station determines the order of assignment of
mobile stations in an RB group as array numbers and reports the
array numbers selected on a per RB group basis as RB assignment
information. For example, as shown in FIG. 8, if RB1 and RB2 form
the first RB group and RB3 and RB4 form the second RB group, as RB
assignment information, the base station only needs to report array
number "1" (mobile station A and mobile station B are assigned to
RB1 and RB2, respectively) or array number "2" (mobile station B
and mobile station A are assigned to RB1 and RB2, respectively) in
the first RB group and reports array number "3" (mobile station C
and mobile station D are assigned to RB3 and RB4, respectively) or
array number "4" (mobile station D and mobile station C are
assigned to RB3 and RB4, respectively) in the second RB group.
[0082] In this way, the base station only needs to report RB
assignment information per RB group, not per mobile station, so
that it is possible to reduce the amount of RB assignment
information. Further, instead of information showing all RB's, only
information showing the order of assignment of mobile stations in
an RB group is demanded as RB assignment information. Further, by
arranging the RB's for data transmission in the same order as the
RB's for transmitting reference signals, it is possible to reduce
the amount of reported information.
Embodiment 2
[0083] When a plurality of RB's are divided into a plurality of RB
groups, if the number of RB's included in one RB group is smaller,
only a smaller number of RB's is required to transmit reference
signals for mobile stations, so that it is possible to decrease the
number of reference signals in the uplink. On the other hand, if
the number of RB's included in one RB group is smaller, the number
of RB's used by mobile stations in each subframe decreases, and so
there is a case where multiuser diversity gain may not be
efficiently achieved. In this way, the number of reference signals
required and the efficiency of multiuser diversity gain are in the
trade-off relationship.
[0084] Generally, for example, the moving speed and position of a
mobile station, the QoS of transmission data and the number of
mobile stations in a communication system vary depending on time,
and so it is preferable to adaptively change the number of RB's
included in one RB group depending on the situation.
[0085] Then, with the present embodiment, the number of RB's
included in each RB group is changed over time.
[0086] FIG. 9 is a block diagram showing a configuration of base
station 300 according to the present embodiment. In the following
description, only differences from Embodiment 1 will be
described.
[0087] Separating section 103 separates a signal outputted from CP
removing section 102 to the reference signal and a data/control
signal, and outputs the reference signal to received quality
measuring section 107 and the data/control signal to frequency
domain equalizing section 104. Further, the number of RB's included
in each RB group varies between subframes, and so RB group
information is inputted to separating section 103 to correctly
separate the reference signal from the received signal. Separating
section 103 specifies the reference signal in the received signal
and separates the reference signal based on the RB group
information.
[0088] RB group controlling section 108 carries out a control for
changing the correspondences between a plurality of RB's and a
plurality of RB groups over time. In this case, RB group
controlling section 108 receives, as input, for example, QoS
information showing the QoS of transmission data, moving speed
information showing the moving speed of each mobile station,
distance information showing the distance between the base station
and each mobile station and information of the number of mobile
stations showing the number of mobile stations present in the
communication system, and carries out a control for changing the
number of RB's included in each RB group based on these pieces of
information.
[0089] For example, recently, services provided in a mobile
communication system range widely from an electronic mail,
television telephone, and delivery of moving images in addition to
a general telephone call, and the communication quality required by
each service varies. Above all, in services such as a telephone
call and television telephone call that require real-time
processing, communication cannot be allowed to stop or delay, and
so it is preferable to carry out frequency scheduling taking into
account the QoS of transmission data. Then, by inputting QoS
information to RB group controlling section 108, RB group
controlling section 108 changes the number of RB's included in one
RB group to satisfy the required QoS.
[0090] Further, it is effective to change the number of RB's based
on moving speed information. For example, when most of the mobile
stations in a communication system are moving at a low speed or are
not moving, there is little fluctuation of received qualities
between several subframes, and therefore, first, the number of RB's
included in one RB group is set comparatively greater and, after
most of the RB's are assigned stably, it is preferable to decrease
the number of RB's included in one RB group to decrease the number
of reference signals. Then, by providing in a mobile station the
moving speed detecting section that detects the moving speed
thereof, this mobile station reports the detected moving speed
information to base station 300. RB group controlling section 108
changes the number of RB's included in one RB group based on the
moving speed information decoded in decoding section 106.
[0091] Further, it is also effective to change the number of RB's
based on the distance between the base station and each mobile
station. For example, when there are a great number of mobile
stations in a close distance to the base station, received power
fluctuates significantly between these mobile stations, and so it
is preferable to stabilize communication by placing an emphasis on
effectively achieving multiuser diversity gain. Then, received
quality measuring section 107 estimates the distance between the
base station and each mobile station based on the received quality
measured in received quality measuring section 107 and RB
controlling section 108 changes the number of RB's included in one
RB group based on distance information.
[0092] Further, it is also effective to change the number of RB's
based on the number of mobile stations communicating with the base
station, that is, the number of mobile stations present in the
communication system. For example, if the number of mobile stations
in the communication system is small, transmitting reference
signals using a great number of RB's does not lead to decreased
throughput, and so the number of RB's included in one RB group may
be set greater.
[0093] FIG. 10 is an operation diagram of the communication system
according to the present embodiment. In subframes 1 and 2, six RB's
(RB1 to RB6) are divided into three RB groups (groups .alpha.,
.beta., and .gamma.), and, in subframe 3, six RB's (RB1 to 6) are
divided into two RB groups (groups .alpha. and .beta.). The base
station decides to switch the number of RB's included in one RB
group using the above information somewhere prior to subframe 3,
and changes the number of RB's to carry out grouping. In subframes
1 and 2, the number of RB's in each RB group is two, and so only
the received qualities of two RB's can be obtained in each
subframe. However, in subframe 3, the number of RB's in each RB
group is three, and so the received qualities of three RB's can be
obtained. For example, if RB's need to be restored to a preferable
arrangement earlier, the number of RB's in the RB group is
increased. Further, if the amount of reference signals needs to be
decreased, the number of RB's in the RB group is decreased. These
are decided by the base station. Further, it is also effective to
transmit reference signals using all RB's at an initial stage and
arrange RB's preferably, and then reduce the amount of reference
signals by decreasing the number of RB's in the RB group.
[0094] As described above, by adaptively changing the number of
RB's included in one RB group depending on the situation, it is
possible to keep the balance between the number of reference
signals and multiuser diversity and build stable communication.
[0095] Further, the number of RB's may be changed by RB group
controlling section 108 based on one of QoS information, moving
speed information, distance information and information of the
number of mobile stations or combinations of these.
[0096] Further, the number of RB's may be changed by RB group
controlling section 108 based on other information. For example, it
is possible to change the number of RB's based on the CQI of each
mobile station or the average CQI.
[0097] Further, if setting of a priority to each mobile station
based on these pieces of information and scheduling according to a
priority in scheduling section 110 are carried out in combination,
it is possible to build stable communication.
[0098] Further, by blending and adaptively changing a case of
forming one RB group with all RB's or a case of forming one RB
group with one RB, it is possible to structure a more flexible
communication system. For example, if the QoS of transmission data
from all mobile stations is higher than a standard at a given time,
it is also effective to form one RB group with all RB's and
transmit reference signals from all mobile stations using all RB's.
Further, by, for example, forming one RB group with one RB having a
CQI higher than the standard, the amount of reference signals may
be reduced.
[0099] Further, it is also effective to carryout optimal RB
assignment by scheduling all RB's on a regular basis and carry out
scheduling by grouping two RB's in one RB group in a subframe in
which RB's are assigned optimally.
Embodiment 3
[0100] The above base station divides a plurality of RB's into a
plurality of RB groups and changes the correspondences between RB's
and RB groups over time. On the other hand, each mobile station
needs to learn the RB's included in each current RB group, and
therefore the base station needs to report RB group information to
each mobile station every time the correspondences between RB's and
RB groups change. However, if RB group information is reported
frequently, the amount of reported information occupying the
downlink increases and downlink throughput is likely to
decrease.
[0101] Then, with the present embodiment, both of the base station
and each mobile station have tables showing the correspondences
between RB's and RB groups and the order of changes in the
correspondences over time.
[0102] FIG. 11 is a block diagram showing a configuration of base
station 400 according to the present embodiment. In the following
description, only differences from Embodiment 1 will be
described.
[0103] Storing section 401 stores a table showing the
correspondences between RB's and RB groups and the order of changes
in the correspondences over time.
[0104] RB group controlling section 108 controls grouping section
109 to change the correspondences between a plurality of RB's and a
plurality of RB groups over time based on the table stored in
storing section 401. On the other hand, the mobile station (not
shown) according to the present embodiment has, in addition to the
components shown in FIG. 5, a storing section that stores the same
table as the table stored in storing section 401 of base station
400, specifies the RB in the RB group to which this mobile station
belongs based on this table and transmits a reference signal to
base station 400 using this RB.
[0105] FIG. 12 shows an example of the table. In this case, the
number of RB's is eight (RB1 to RB8). This table divides eights
RB's (RB1 to RB8) into four RB groups (groups .alpha., .beta.,
.gamma. and .zeta.), and, in a given subframe N, RB1 and RB2, RB3
and RB4, RB5 and RB6, and RB7 and RB8 each belong to the same
group. In the next subframe N+1, RB2 and RB3, RB4 and RB5, RB6 and
RB7, and RB8 and RB1 each belong to the same group. Then, when the
group comes to the bottom of the table, the group returns to the
top. That is, in the next subframe N+2, grouping of subframe N is
employed.
[0106] In this way, with the present embodiment, the
correspondences between RB's and RB groups and patterns of changes
in the correspondences are set in the table, and RB group
controlling section 401 carries out a control for changing the
correspondences between a plurality of RB's and a plurality of RB
groups over time based on this table.
[0107] FIG. 13 shows another table. This table is set such that
adjacent RB's do not belong to the same RB group successively. To
be more specific, in this table, each of RB1 to RB8 belongs to the
same group once with each of the other seven RB's in one round, and
the RB which is apart from the RB of the current pair is
preferentially selected as the RB of the next pair.
[0108] For example, in subframe N, the mobile station assigned to
RB1 also arranges the reference signal in RB5 which is apart from
RB1 by 1/2 of all eight RB's. Further, the mobile station assigned
to RB5 arranges the reference signal in RB1 which is apart from RB5
by 1/2 of all eight RB's. The same applies to the other RB's.
According to these arrangements, the reference signals of all
mobile stations are arranged in two RB's which are apart from each
other by 1/2 of all RB's.
[0109] Further, in subframe N+1, the mobile station assigned to RB1
also arranges the reference signal in RB3 which is apart from RB1
by 1/4 of all eight RB's. Further, the mobile station assigned to
RB3 also arranges the reference signal in RB1 which is apart from
RB3 by 1/4 of all eight RB's. The same applies to the other
RB's.
[0110] Further, in subframe N+2, the mobile station assigned to RB1
also arranges the reference signal in RB7 which is apart from RB1
by 1/2 of all eight RB's according to assignment in subframe 2.
Further, the mobile station assigned to RB7 also arranges the
reference signal in RB1. The same applies to the other RB's.
[0111] Further, in subframe N+3, the mobile station assigned to RB1
arranges the reference signal in RB2 which is apart from RB1 by 1/8
of all eight RB's. Further, the mobile station assigned to RB2
arranges the reference signal in RB1 which is apart from RB1 by 1/8
of all eight RB's. The same applies to the other RB's.
[0112] The same processing is carried out in subframes N+4 to N+6
and so will not be described.
[0113] In this way, each mobile station is able to compare RB's in
order from RB's which are more likely to show little frequency
correlation and so is able to select a preferable RB's earlier.
[0114] As described above, according to the present embodiment, the
base station and mobile station each have a common table in which
the correspondences between RB's and RB groups and the order of
changes in the correspondences over time are set, and so RB group
information needs not to be reported, so that it is possible to
improve downlink throughput.
Embodiment 4
[0115] As described above, by providing a common table both in the
base station and mobile station, RB group information needs not to
be reported, so that it is possible to improve downlink throughput.
However, patterns of rearrangement of RB groups are fixed to the
patterns set in the table, and so, depending on the situation of
communication, cases occur where adequate rearrangement is not
possible.
[0116] Then, with the present embodiment, to efficiently achieve
multiuser diversity gain in various communication situations, a
plurality of tables matching situations of communication are stored
in the base station and mobile station in common and are adaptively
switched depending on the situation of communication.
[0117] FIG. 14 is a block diagram showing a configuration of base
station 500 according to the present embodiment. In the following
description, only differences from Embodiments 1 to 3 will be
described.
[0118] Separating section 103 separates the signal outputted from
CP removing section 102 to the reference signal and a data/control
signal, and outputs the reference signal to received quality
measuring section 107 and the data/control signal to frequency
domain equalizing section 104. Further, the number of RB's included
in each RB group varies between subframes, and so RB group
information is inputted to separating section 103 to correctly
separate the reference signal from the received signal.
[0119] Storing section 501 stores a plurality of tables showing the
correspondences between RB's and RB groups and the order of changes
in the correspondences over time. One or both of the
correspondences and the order of changes varies between these
plurality of tables. Further, these plurality of tables may be
configured to be stored in advance or added or updated from outside
base station 500.
[0120] RB group controlling section 108 controls grouping section
109 to change the correspondences between a plurality of RB's and a
plurality of RB groups over time based on the tables stored in
storing section 501. In this case, RB group controlling section 108
receives as input, for example, QoS information, moving speed
information, distance information, information of the number of
mobile stations, CQI information showing the CQI of each mobile
station or the average CQI and switches the table to be used, based
on these pieces of information. Further, RB group controlling
section 108 generates switching report information to report to
each mobile station that the table to be used has been switched,
and outputs this information to encoding section 111.
[0121] On the other hand, the mobile station (not shown) according
to the present embodiment has, in addition to the components shown
in FIG. 5, a storing section that stores a plurality of same tables
as a plurality of tables stored in storing section 501 of base
station 500 and a controlling section that carries out a control
for switching the table to be used, and switches the table to be
used, to the same table used in base station 500 according to
switching report information reported from the base station.
[0122] Further, there is, for example, a specific switching method
where different table numbers are allocated to a plurality of
stored tables, base station 500 reports one of the table numbers to
the mobile station as switching report information and the mobile
station selects the table to be used, based on the reported table
number.
[0123] In this way, according to the present embodiment, uplink
frequency scheduling can be adaptively carried out depending on the
situation of communication, and switching report information only
needs to be reported only when the table is switched, so that it is
possible to reduce the amount of downlink reported information.
Embodiment 5
[0124] Generally, there are a plurality of mobile stations of
difference moving speeds in the communication system. In this case,
the fluctuation of fading over time is moderate in mobile stations
of low moving speeds. Consequently, in terms of improvement of
uplink throughput, preferably, a mobile station determines the
transmission interval between reference signals based on the moving
speed, and, based on decision in the mobile station, selects
whether "to transmit the reference signal" or "to transmit data" in
a region where the reference signal is assigned by the base
station.
[0125] With the present embodiment, the mobile station detects the
moving speed thereof and adaptively changes an arrangement of the
reference signal and transmission data according to the detected
moving speed.
[0126] FIG. 15 is a block diagram showing a configuration of mobile
station 600 according to the present embodiment. In the following
description, only differences from Embodiment 1 will be
described.
[0127] Moving speed detecting section 601 detects the moving speed
of the mobile station 600 and generates moving speed
information.
[0128] Transmission target determining section 602 determines
whether to transmit the reference signal or to transmit data in the
region where the reference signal is assigned, using the moving
speed information and RB group information. To transmit the
reference signal, transmission target determining section 602
reports the arrangement of the reference signal to reference signal
arranging section 206, and to transmit data, reports the
arrangement of transmission data to RB specifying section 208.
[0129] FIG. 16 shows the operation diagram of the communication
system according to the present embodiment. In this case, the
number of RB's is four (RB1 to RB4), and there are four mobile
stations A to D of different moving speeds. Further, in portions
shown by underlined A to D of FIG. 16, the received qualities
fluctuate little over time, and the received qualities in these
portions and the received qualities measured up to earlier
subframes are almost equal.
[0130] The mobile station is able to predict the fluctuation of
received quality over time from the detected moving speed and
decide the transmission interval between the reference signals. For
example, if the moving speed of mobile station C is low, mobile
station C does not need to update the received quality for three
subframes and is able to decide that the reference signal needs not
to be transmitted using the assigned RB. Based on this decision,
the mobile station determines whether to transmit the reference
signal or transmit data in a region assigned by the base station
for the reference signal.
[0131] Further, if the reference signal is not arranged in the
received signal, the base station may decide that the received
signal is data, or may perform decision by adding bits showing
whether a data signal from the mobile station is the reference
signal or data, to the data signal. Further, based on the
scheduling result in an earlier subframe, the base station is able
to decide which RB is used by a mobile station of a low speed to
transmit the reference signal, and therefore may decide whether a
signal to be transmitted is transmission data or the reference
signal based on this decision. For example, in a case where a given
mobile station moves at a low speed, does not transmit the
reference signal using the same RB in three subframes and instead
arranges transmission data in RB's, the base station checks within
the three subframes whether there is a reference signal transmitted
by the mobile station using the RB's, and, if there is, utilizes
the received quality of this reference signal again. In this case,
the moving speed range and the transmission interval between
reference signals matching this moving speed range are set in
advance, and, only when the transmission interval changes following
changes in the moving speed, each mobile station may report the
changes in the transmission interval, to the base station.
[0132] Further, the mobile station may measure the fluctuation of
received quality over time instead of the moving speed, and
determine whether to transmit the reference signal or transmit data
based on this measurement value.
[0133] In this way, according to the present embodiment, a mobile
station changes the transmission interval between reference signals
based on the moving speed thereof, so that the mobile station is
able to replace unnecessary reference signals with data and improve
throughput.
Embodiment 6
[0134] For some structures of the communication system, the
bandwidth used in each mobile station is not even, and there are a
plurality of mobile stations using different bandwidths in one
communication system. In this situation, grouping of RB's and
scheduling are likely to be complicated. Consequently, in this
situation, it is preferable to bring together a plurality of mobile
stations using narrow bandwidths as one mobile station and make the
RB bandwidths even.
[0135] Then, with the present embodiment, scheduling section 110 of
the base station brings together into one a plurality of mobile
stations that use narrower RB bandwidths than the standard RB
bandwidth and carries out scheduling by making the RB bandwidths
even.
[0136] FIG. 17 is an operation diagram of the communication system
according to the present embodiment. FIG. 17 shows a case where
there are mobile station A that carries out communication using a
bandwidth of 2.5 MHz and mobile station C and mobile station D that
carry out communication using a bandwidth of 1.25 MHz. Further, 2.5
MHz is the scheduling standard, and mobile station C and mobile
station D are brought together and are used as one set with the
bandwidth of 2.5 MHz. That is, the base station assigns the regions
for transmitting reference signals to the RB group including mobile
station A and mobile stations C+D (the number of RB's in the RB
group is two), and reports the result to each mobile station. The
base station measures the received qualities of these reference
signals and assigns regions for transmission data of mobile
stations. The transmission data region assignment pattern can be
selected from the three assignment patterns in FIG. 17.
[0137] In this way, according to the present embodiment, if there
are a plurality of mobile stations using different bandwidths, by
bringing together as one set a plurality of mobile stations that
use narrower bandwidths than the standard and making their
bandwidths even to the standard bandwidth, it is possible to
efficiently carry out scheduling.
[0138] Embodiments of the present invention have been
described.
[0139] Further, although the above embodiments have been described
assuming single carrier transmission where there are a plurality of
RB's, the present invention is not limited to this, and each mobile
station may arrange using frequency division multiplexing or
multicarriers the reference signal in the RB to which each mobile
station is assigned, and transmit a reference signal.
[0140] Further, although a case has been described with the above
embodiments where reference signals are transmitted at a plurality
of times in one subframe, for example, at times Tn and Tn+1 in FIG.
7, the present invention is not limited to this. For example, a
reference signal may be transmitted at a given time in the first
subframe, and another reference signal may be transmitted at a
given time in the second subframe following the first subframe.
That is, by using a plurality of RB's over a plurality of subframes
as one RB group, combinations of RB's forming the RB group may be
changed overtime. In this way, reference signals may be transmitted
at a plurality of times over a plurality of subframes.
[0141] Further, if reference signals are transmitted at a plurality
of times over a plurality of subframes as described above, data of
the first subframe maybe assigned to the RB of a high received
quality, that is, to the RB of received quality 2 in case of
received quality 1<received quality 2, and data of the second
subframe may be assigned to the RB of a low received quality, that
is, to the RB of received quality 1 in case of received quality
1<received quality 2. Further, the reference signals and data
may be transmitted using the same RB between subframes. Further, in
a plurality of subframes, the reference signals maybe transmitted
using a plurality of RB's included in the RB group and data may be
transmitted using one of a plurality of RB's included in an RB
group.
[0142] Further, a plurality of subframes in the above embodiments
may be continuous or discontinuous.
[0143] Further, in scheduling to assign RB's to a plurality of
mobile stations in the RB group, the RB's may be assigned such that
the received qualities of all of a plurality of mobile stations
increase or the RB's may be assigned based on the received quality
of one specific mobile station in a plurality of mobile stations.
For example, in a RB group, based on the received quality of a
mobile station of a high priority, RB's may be assigned to a
plurality of mobile stations including other mobile stations of
lower priorities.
[0144] Further, received quality is not limited to the SINR, and
the SIR, SNR, CIR, CNR, CINR, RSSI, received intensity, received
power, interference power, error rate, transmission rate,
throughput, the amount of interference or MCS that realizes a
predetermined error rate may be used as received quality. Further,
the CQI may be used as received quality.
[0145] Furthermore, the base station and mobile station according
to the above embodiments may be referred to as Node B and UE,
respectively.
[0146] Each function block employed in the description of each of
the above embodiments may typically be implemented as an LSI
constituted by an integrated circuit. These may be individual chips
or partially or totally contained on a single chip. "LSI" is
adopted here but this may also be referred to as "IC," "system
LSI," "super LSI," or "ultra LSI" depending on differing extents of
integration.
[0147] Further, the method of circuit integration is not limited to
LSI's, and implementation using dedicated circuitry or general
purpose processors is also possible. After LSI manufacture,
utilization of a programmable FPGA (Field Programmable Gate Array)
or a reconfigurable processor where connections and settings of
circuit cells within an LSI can be reconfigured is also
possible.
[0148] Further, if integrated circuit technology comes out to
replace LSI's as a result of the advancement of semiconductor
technology or a derivative other technology, it is naturally also
possible to carry out function block integration using this
technology. Application of biotechnology is also possible.
[0149] The disclosure of Japanese Patent Application No.
2006-099914, filed on Mar. 31, 2006, including the specification,
drawings and abstract, is incorporated herein by reference in its
entirety.
INDUSTRIAL APPLICABILITY
[0150] The present invention is applicable for use in, for example,
a mobile communication system.
* * * * *